Consistency when measuring and counting the symbols on your plans will help you reduce the time it takes to estimate a job and eliminate some errors.
Counting and measuring the symbols shown on a project's electrical plan is a critical step in the development of an accurate estimate. This task, known as a takeoff, requires you to follow an orderly, organized, methodical routine - complete with proper forms, colored pencils or pens, and a counter. It's important to understand how to incorporate these elements effectively to ensure a proper takeoff. Let's review each step of the process to help you maintain consistency in your estimating efforts.
Forms. Proper forms and work sheets save time, create consistency, and assist in the reduction of errors. The forms and work sheets also help serve as a reminder of items you may accidentally omit.
Different types of construction styles, such as residential, commercial, or industrial, lend themselves to different types of estimating forms or work sheets. For example, a work sheet used to determine the lighting requirements is different from the work sheets used to record the feeders and service equipment requirements. You can design your own work sheets or order them from reputable sources like the National Electrical Contractors Association (NECA).
Colored pencils. Use colored pencils or pens to identify each item on the plan you are counting or measuring. Once you've finished this task, your blueprints should be a color representation of the electrical work required to complete the job.
If you attempt to estimate a job without color marking the blueprints, you're more likely to make a mistake. If someone doesn't want you to mark up the blueprints, you could go to a copy center and make a copy for yourself at 100% scale. You could also place a large plastic film over the blueprints to mark on.
Counting symbols. The purpose of counting symbols is to identify the true quantity of components required for the job. When counting, you must be capable of reading and interpreting all blueprint symbols and notes. You must also understand the language on the drawings and specifications.
When you count symbols, use a handheld counter to keep track of the count. After you've counted a symbol, mark it with a colored pencil or pen to make sure to count it only once.
Measuring circuits. Prior to measuring any circuits, verify the architectural scale listed in the blueprints. Test the scale to ensure its accuracy. A blueprint is sometimes duplicated at a copy center at a reduced size, which will throw off all of your measurements.
You can find most scale dimensions in the title block of drawing; however, the scale might be different on different pages. If you're not careful, your measurement can be off by as much as 100%.
Tools used to measure circuit lengths include an architectural ruler, a scaled measuring tape, a mechanical measuring device, or an electronic measuring wheel. The architectural rule is fine for a few quick measurements. Measuring tape for 1/8-in. and 1/4-in. scale drawings is popular; however, the electronic scale wheel is the most convenient and most accurate when working with drawings that have multiple scales.
Once you have counted the fixtures, switches, and convenience receptacles, you can measure the branch circuit wiring for each of these outlets. When you measure each run, don't forget to consider the drops for the switches, receptacles, and panel.
Many estimators will place a scaled line on the blueprint to represent the distance of the drops. This way, when they come across a drop for a switch, they simply scale the distance from the pre-scaled line. Some electronic scale wheel devices permit you to press one key to add a constant distance for drops. But if your drops are of different lengths, make sure you reset the constant for each measurement.
When you measure branch circuits, be sure to take off the 2-wire circuits first, the 3-wire circuits next, and then the 4-wire circuits. After you have measured a circuit, trace the line with a colored pen or pencil. It doesn't matter what color you use, just be consistent (i.e. 2-wire - yellow; 3-wire - blue; etc.).
If the working drawings do not indicate the circuit layout or wiring configuration, you must perform this task first and then measure the circuit wiring.
Take off sequence. Although you'll find no set sequence for performing the takeoff, consistency will help you reduce the time it takes to estimate a job and help you to eliminate some errors. The following are three typical takeoff sequences.
One section/page at a time. Taking off one page of the blueprint at a time, or all of the wiring of the first floor, second floor, etc. This method is excellent if you use a computer, but impractical if you estimate manually.
Start at service and end with lighting. With this method, you start the takeoff at the utility service location. Then, you continue by taking off the feeders, branch circuits, and lighting fixtures. This method is time consuming and requires many movements between many pages of drawings.
Start with lighting and end with the service. With this method, you start the takeoff with the lighting fixtures and finish it with the service equipment. This approach generally follows this sequence:
• Count lighting fixtures and develop quantities for quotes,
• Count switches,
• Count receptacles,
• Measure branch circuit wiring,
• Count and measure individual branch circuits and home runs. Develop quantities for switchgear quotes,
• Count and measure special systems such as television, phone, Cat. 5, alarm, security sound, etc., and
• Count panels and measure feeders, service runs, service equipment. Develop quantities for switchgear quotes.
This method permits a quick overview of the job and eases you into the estimate. After taking off the homeruns and special circuits, you should have a good idea of the scope of the project. This should enable you to deal with more complex (and expensive) portions of the takeoff.
With a proper takeoff, you should have no need to refer to the plans or specifications when determining the bill-of-material for the project. Of course, it's best to develop a system that fits your personal style and needs. But whatever system you develop, be sure to use the same procedures every time you estimate a job.